Seven is the one amount D for which the equation 2n − D = x2 has in excess of two options for n and x purely natural. In particular, the equation 2n − seven = x2 is recognized as the Ramanujan–Nagell equation. Obviously There's also the nicely-regarded Tale of Pharaohs https://best-pool-exercise-equipm31615.life3dblog.com/36546014/everything-about-7-day-pill-organizers